1. Field of the Invention
This invention relates to a camera capable of divided photometry in which a visual field is divided into two or more regions and the luminance of incident light is measured in every region. More particularly, the invention relates to a camera having an electronic solid-state image device, such as a still-video camera (an electronic still-video camera) which records a still-video signal on a video floppy, a digital still-camera in which a still-video signal is converted into digital image data that is then stored in a memory, a movie video camera, etc.
2. Description of the Related Art
In divided photometry, there are various methods through which the area in a visual field can be divided. One is to perform photometry upon dividing luminance into that of the central portion of a visual field and that of the background of the field. This is suited to photographic composition in which the subject is a person and the subject is placed substantially at the center of the visual field. The luminance of the central portion is referred to as the spot photometric value or spot luminance, and the average luminance of the background and central portion is referred to as the average photometric value or average luminance.
In order to obtain an appropriate photographic image, it is necessary to consider the difference (luminance difference) between the spot luminance and the average luminance. For example, in a case where a small subject at the central portion is dark and the background is bright, the background will appear almost white if exposure is controlled in conformity with the luminance of the subject. This problem becomes particularly pronounced since dynamic range is comparatively narrow in a camera equipped with a solid-state electronic imaging device, such as a CCD, as the imaging means.
Thus, in order to obtain a suitable photographic image, it is necessary to change the photographic mode (i.e., exposure control based upon spot luminance, exposure control based upon average luminance, whether a strobe light emission is necessary, whether backlight control, described later, is necessary, etc.) in dependence upon the luminance difference between spot luminance and average luminance. At such time, it is necessary to take into consideration the fact that the luminance difference varies depending upon distance as well. For example, in a case where the subject is nearby, spot luminance represents the luminance of the subject. However, if the subject is in the distance, the subject appears small and the background also enters the spot-luminance measurement area of the photometric element. As a result, spot luminance no longer represents the luminance of the subject correctly.
Furthermore, in a camera having a solid-state electronic imaging device as an imaging means, the video signal is displayed on a display unit such as a CRT as is (though the signal is temporarily stored on a recording medium). As a result, it is necessary to detect absolute luminance correctly and to perform exposure control conforming to the absolute luminance.